asn1tostruct: allow to override build date

in order to make builds reproducible.
See https://reproducible-builds.org/ for why this is good
and https://reproducible-builds.org/specs/source-date-epoch/
for the definition of this variable.

Also do not record build user name to not have it vary.

Change-Id: I5cfa465cc82f009f28dd7f12ced0e72a05fda842

asn1/utils/asn1tostruct.py

@@ -4,6 +4,7 @@ import re, os, sys, string
 import datetime
 import getopt
 import getpass
+import time
 
 version = "0.5osmo1"
 
@@ -33,11 +34,11 @@ def printDebug(string):
         print string
 
 def outputHeaderToFile(f, filename):
-    now = datetime.datetime.now()
+    now = datetime.datetime.utcfromtimestamp(int(os.environ.get('SOURCE_DATE_EPOCH', time.time())))
     f.write("/*******************************************************************************\n")
     f.write(" * This file had been created by asn1tostruct.py script v%s\n" % (version))
     f.write(" * Please do not modify this file but regenerate it via script.\n")
-    f.write(" * Created on: %s by %s\n * from %s\n" % (str(now), getpass.getuser(), filenames))
+    f.write(" * Created on: %s\n * from %s\n" % (str(now), filenames))
     f.write(" ******************************************************************************/\n")
 
 def lowerFirstCamelWord(word):